Q.If dentistry had existed 50,000 years ago, what problems would have sent our Neanderthal and Cro-Magnon ancestors to the doc? –D. J. Bickers

A. "Well, not tooth decay, because that would be very rare on a hunter-gatherer diet," says Loyola University of Chicago anthropologist James M. Calcagno. However, expect long lines for root canals, due to people wearing down their enamel on the raw, gritty foods, and exposing their pulp cavities, which just had to hurt! (Eventually they'd wear down the nerves too, and chew with the stumps and roots.)

Demand for hygienists would be great, to deal with plaque and periodontal disease. There'd be abscesses untold, and swollen faces and throats from the infections, but alas antibiotics would still be over 49,900 years away and some of the infections would be hard to stop, progressing from the patient's oral cavity into the circulatory system and maybe up to the brain or down to the heart and lungs (or if lucky staying in the mouth, better for the health but bad for the breath).

Forget small tidy offices– field hospitals would be more like it. "It wouldn't be a pretty picture. What we deal with today is a picnic by comparison."

Q.Could a newborn baby, beefed up on steroids while in the womb, hang by both hands gripping a bar suspended over the Grand Canyon? –B. Huey

A. Forget the steroids. This fantastic "thought experiment" is actually well within a baby's physical capability. Just make it a bar about the thickness of Mom's finger, and blindfold baby so as to prevent triggering the visual cliff reflex (inborn fear of heights), which might throw our little hero into a grip-loosening fit.

A newborn's gripping reflex around a finger pressed into each palm is so strong, says Spencer Rathus in Essentials of Psychology, 5th Edition, that he or she could be lifted right out of the cradle to hang in midair.

Q.UFOs have been reported making 90-degree directional shifts, in effect turning on a dime in the heavens. Why don't human pilots add this eye-catching maneuver at air shows? –C. Yeager

A. In an "X-Files" episode, Air Force pilots tried this using an alien craft and found their bodies couldn't hack it because the forces were too great, says physicist Lawrence M. Krauss in Beyond Star Trek.

A realistic touch! Assuming a Mach 2 craft decelerates in .1 second before veering sideways–fast enough that it might be perceived as instantaneous by observers– 700 g's would be required. That's like carrying 35 tons on the shoulders! Ordinarily, 8 g's is the tolerance limit.

The craft itself would also feel the crunch. Imagine a plane losing power at 1,000 feet and crashing a meter deep into the earth. The collision forces here, says Krauss, are roughly 2,800 g's, or only four times the right-angle. "Judging from what most plane crashes look like, I would suggest no craft made out of mere metal would be likely to survive the X-Files-type acrobatics for long."

How about superstrong metals of advanced civilizations? Okay, maybe, but as for the aliens themselves withstanding g-forces of right-turn magnitude, "I don't see how, unless they evolved in an environment featuring 40-ton raindrops."

Q.Two college students show up late together for an exam, alibiing that they had a flat tire. The cagey prof takes each of them aside and asks, "Which tire was it?" Strategically, how should they answer? –B. F. Goodyear

A. Wonderful story! It could've happened but is probably an urban legend, recounted in the "Ask Marilyn" column. A reader had suggested that since each of the students must guess 1 tire out of 4, the likelihood of both picking the same tire is 1 out of 16. But, said Marilyn, this exaggerates their dilemma. Whichever tire one of them picks, the other has a 1-in-4 chance of matching it.

Dartmouth's "Chance News" took the matter a step further. Is the students' predicament really as bad as 1 in 4? Citing something called a "Schelling point," Roger Koppl noted that there are certain places, numbers, ratios, etc., that take on a special prominence in the mind: Separated from a friend while vacationing in Paris, and having made no prior arrangements, where would you go to meet back up? Sure, try the Eiffel Tower.

A quick survey revealed that when people are asked to name one of a car's four tires, most (62 percent in this instance) singled out "right front." So if the tardy duo keep their wits about them, odds are they'll come out okay.